Cotton treating process

ABSTRACT

A process is disclosed for the heat treatment of cotton yarn to improve its tensile strength and elongation. The yarn is heated in the absence of substantial tension on the yarn to a temperature above its shrinkage temperature and permitted to shrink without substantial yarn tension. The yarn is thereafter cooled to set the same.

United States Patent [1 1 Rendall et al.

[ Sept. 24, 1974 COTTON TREATING PROCESS [75] Inventors: John L. Rendall; William Q. Rhyne;

Arthur Williams, all of Greenville, SC.

[73] Assignee: The Richen Co., Inc., Greenville,

[22] Filed: Feb. 9, 1972 [21] Appl. No.: 224,765

[52] U.S. Cl. 28/72 HR, 28/72.l7 [51] Int. Cl. D02j 1/22 [58] Field of Search 28/72 HR, 72.17, 76

[56] References Cited UNITED STATES PATENTS 3,729,831 5/1973 Kosaka et al 28/72 HR Primary ExaminerLouis K. Rimrodt Attorney, Agent, or FirmLyon & Lyon [5 7 ABSTRACT A process is disclosed for the heat treatment of cotton yarn to improve its tensile strength and elongation. The yarn is heated in the absence of substantial tension on the yarn to a temperature above its shrinkage temperature and permitted to shrink without substantial yarn tension. The yarn is thereafter cooled to set the same.

9 Claims, 4 Drawing Figures COTTON TREATING PROCESS BACKGROUND OF THE INVENTION Yarn composed of cotton fibers is very desirable for the production of clothing and other items where a soft surface is desired. Cotton, however, is susceptible to breakage due to its relatively low tensile strength-To overcome this disadvantage, cotton is blended with synthetic fibers to provide a yarn which has sufficient strength to withstand processing such as dry cleaning and machine washing and drying.

Moreover, garments having permanent press qualities are today quite popular. Since such garments are manufactured by impregnating the fabric with a thermally reactive agent and curing the garment by the application of heat to insolublize the reactive agent, as described in Warnock et al. US. Pat. No. 2,974,432, such processing imposes additional requirements upon cotton fibers. It has been found that as the crease resistance or durable press properties of cotton fabrics are improved, the strength and resistance to abrasion deteriate. In order to counteract such loss in strength and abrasive resistance, it is necessary to reinforce the cotton with synthetic fibers.

When cotton fibers are blended with synthetic fibers, an intimate blend of the fibers is required to provide yarn having sufficient strength for the production of satisfactory garments, especially when the garments are to be subjected to permanent press treatment. One consequence of this, of course, is a sacrifice in terms of the softness of the surface of the resulting garment, since the exposed fabric surface is thus composed of synthetic as well as cotton fibers. It is accordingly, clearly desirable to provide cotton yarn of increased strength and elongation capability in order to'be suitable for the production of garments without the necessity of blending synthetic fibers therewith.

SUMMARY OF THE INVENTION The present invention is thus directed to a process of heat treating cotton yarn in which the yarn is heated to a temperature above its shrinkage temperature and permitted to shrink in the absence of substantial yarn tension. The yarn is thereafter cooled to set the same. It has been found that the set yarn is of increased tensile strength and also elongation capability.

DESCRIPTION OF PREFERRED EMBODIMENTS In the drawings:

FIGS. 1 and 2 are micro-photographs of cotton yarn before and after treatment by the process of this invention; and

FIGS. 3 and 4 illustrate a preferred embodiment for carrying out the process of this invention, FIG. 3 being a diagramatic fragmentary perspective view illustrating the general process and apparatus to perform such process, and FIG. 4 being an enlarged fragmentary view illustrating a portion of the heat treating apparatus.

Referring more particularly to FIGS. 1 and 2, it will be observed from FIG. Zthat cotton yarn treated in accordance with the present invention has a different cross-sectional structure than the untreated cotton yarn of FIG. 1. The structure shown in FIG. 2 is clearly more ordered indicating a definite reorientation of the fibers resulting from the heat treatment. In spite of the more ordered structure, however, as will be shown by the illustrative examples which follow, the treated yarn not only has greater tensile strength than the untreated yarn, but also has greater elongation capability, which is quite surprising.

As stated previously, to obtain set yarn having the structure shown in FIG. 2, the cotton yarn is heated in the absence of substantial tension on the yarn to a temperature above its shrinkage temperature, generally within the range of from about 400F. to about 460F. The heated yarn is permitted to shrink also without substantial tension on the yarn, and is thereafter cooled, ultimately to room temperature, to set the yarn in its reoriented structure.

Only a relatively short heating time is required to effect the desired temperature elevation and shrinkage, normally from approximately 5 to about 10 seconds. The length of heating may, of course, be varied somewhat depending upon the way the heat is applied to the yarn. In a preferred form of the process, as described hereinafter, the yarn is heated by the application of radiant heat, which permits suitable processing at the temperatures and times referred to above.

Since cotton fibers are susceptible to degradation due to the influence of high temperature, in some instances it may be desirable to impregnate the yarn with a chemical solution prior to heating to help prevent degradation. Examples of suitable such substances include aqueous solutions of ethylene glycol and diethylene glycol. It is only necessary to use relatively small percentages of such substances, as for example, approximately 1 or 2 percent solutions. Similarly, the yarn has to take up only a sufficient quantity to keep the cotton fibers moist at the processing temperatures. Ordinarily, a pickup of approximately 5 to about 20 percent of the solution during impregnation is sufficient.

The yarn may also be impregnated with a chemical solution containing a cellulose crosslinking agent to cause the cotton fibers to undergo crosslinking when the yarn is subsequently heated in an effort to provide additional strength to the cotton fibers, thereby contributing to the production of yarn having an even greater overall strength. Examples of suitable such materials include aqueous solutions of commonly used cellulose crosslinking agents, such as formaldehyde, urea-formaldehyde, methylol melamine resins, di methylol dihydroxy ethylene urea (DMDHEU) etc. Such solutions will also be catalyzed with any of the usual catalysts, such as zinc nitrate, ammonium chloride, hydrochloric acid etc. Examples of acceptable solutions are:

Solution No. 1

4,000 cc water, 1,000 cc 37 percent formaldehyde, grains ammonium chloride.

Solution No. 2

4,000 cc water, 1,000 cc 37 percent formaldehyde, 280 grains ammonium chloride.

Solution No. 3.

4,000 cc water, 2,000 cc formaldehyde (37 percent), 280 grains ammonium chloride.

The yarn may be impregnated, irrespective of whether a cross-linking or moistening solution is used, by any of the standard impregnation techniques, such as dipping, spraying, or passing the yarn in a continuous manner through a bath of the desired solution.

Referring now to FIGS. 3 and 4, a preferred form of the process and apparatus for carrying out the process are illustrated. Such apparatus is the subject of copending application Ser. No. 880,744, which is assigned to the same assignee as the present application, and includes means to feed the yarn from a supply cone 1 including a feed roll 2 and a pressure roll 3. The feeding means also includes a stop motion micro-switch 4 and solenoid 5 to control movement of the yarn to stop feeding if the yarn stops moving through the apparatus. The yarn is thus fed into a nozzle designated generally by the numeral 6 (FIG. 4) enclosed within housing 7 from which it is introduced into a tubular conduit and heated as will be described. After the yarn has travelled through the heating unit, it exits through a nozzle 11 and into a cooling means 12 in which the yarn is permitted to accumulate to facilitate cooling and setting. The yarn is withdrawn from the cooling means by rewinding apparatus 14, with the rate of rewinding being correlated with the dwell time within the cooling reservior to permit the yarn to remain within the cooling means for a sufficient time for adequate cooling and setting. As the yarn is removed from the cooling means, it is passed under bar 15 positioned adjacent to the trough 16, whereby sufficient tension is exerted on the yarn to remove snags or kinks which may have developed during cooling.

In FIG. 4, the heating unit is shown in detail. As the yarn enters the first nozzle 6, it is contacted with heated air which is injected into the nozzle through line 22. The temperature of the air injected into the nozzle 6 will, of course, vary depending upon the blend of yarn being processed but will be within the range of from approximately 200F. to about 500F. The heated air thus helps to raise the temperature of the yarn to the necessary temperature for processing and also to move the heater 30 to regulate properly the temperature of air passing through the yarn tube.

The tubular conduit 21 is disposed, as shown, in a plurality of convolutions 40 about the tank 33. As the yarn passes through the tubular conduit, it is heated by the application of radiant heat from tank 33 and the electrical heating means 36. The temperature required within the convoluted conduit to shrink and bulk the yarn will vary depending upon the type of cotton being processed. The temperature will be at least approximately 400F and preferably approximately 425.F'up to about 460F. or 475F. By the same token, the rate of travel of the yarn through the tubular conduit affects somewhat the temperature which is necessary to achieve-the desired shrinkage and bulking (the faster the yarn travels, the higher the temperature which is necessary). The rate of travel is also variable and is dependent upon the size of the tubular conduit, the pressure of the heated air injected into the inlet nozzle and the pressure differential between the inlet and outlet nozzles, since the yarn desirably is disposed substantially centrally within the tubular conduit without contacting the wall. In general, in using a inch diameter tubular conduit, the feed rate of the yarn will be from about 100 to about 500 yards per minute and the pressure of the injected air from about 5 to about 20 psig at the inlet nozzle and from about 2 to about 2 to about 5 psig at the exit nozzle.

The exit nozzle 11 includes means designated by numeral 41 for injecting cold air into the nozzle to contact the hot yarn passing therethrough. The cold air reduces the yarn temperature from the processing temperature to approximately l25F. or lower. The yarn undergoes further cooling to approximately room temperature yarn through the convoluted tubular conduitwhile in wlthm cgolmsumt a substantially relaxed or tensionless condition. After The mvenqon W111 f bettef y reference travelling through the tubular conduit, the yarn passes to the following Speclfic but lllustfatlve examplesthrough the exit nozzle 11 and into the cooling unit 12 as previously described. EXAMPLE 1 A gun type heater 30 is connected to tube 31, which I connects with line 22 to inject heated air into the noz- Using the apparatus and process previously described zle 6. The preheated air is fed into the gun heater with respect to FIGS. 3 and 4, 100 percent cotton yarn through line 32, being supplied from tank 33 in which having a cotton count of 10/5 was treated under the the air is introduced through line 34 by control valve conditions shown in Table l, with the speed of travel 35. If desired, heating means such a gun heater can also of the yarn through the apparatus varying from to be connected to line 34 to heat the air supplied to the 125 yards per minute, and the processing temperature tank to assist in providing more uniform application of from 400 to 425F. Sample No. l was a control, that heat to the yarn during processing. For the same puris untreated cotton yarn, included for comparison purpose, electrical heating means 36 are provided to help 50 oses, As shown in Table 1, there was a significant gain provide heat to the tubular conduit. Sensing means 37 in tensile strength and elongation in the yarn treated in is positioned in the yarn tube 38 which senses the temaccordance with the present invention. The treated perature of the air passing through the yarn tube. The yarns also exhibited a uniformly smooth soft hand and sensing device, of course, is connected to a control (not compared favorably in all respects with the untreated shown through lead 39 and correlated with the gun n- 1 S l N 1 TABLE I COTTON 10/5 COTTON COUNT APPL I20 YD. STRENGTH NO. YPM F. SOLNP SPEED SKEIN GRAINS GRAMS ELONG HAND & APPEAR. RANK l CONTROL 100 588 7.5 5 2 I25 400 DRY 96 699 8.6 l 3 400 A SLOW 98 702 9.5 l 4 I25 400 A FAST 98 636 8.2 2 5 400 A FAST 96 6l0 8.l 4

TABLE I 100% COTTON 10/5 COTTON COUNT APPL 12 YD. STRENGTH NO. YPM F. SOLN. SPEED SKElN GRAINS GRAMS ELONG HAND & APPEAR. RANK 6 50 425 A FAST 97 731 8.7 4 7 50 425 DRY 97 682 8.5 3 8 100 425 B FAST 96 678 8.2 2 9 100 425 C FAST 90 589 7.3 4discolored 50 425 C FAST 90 551 7.3 4discolored Bath Formulations for A, B and C as follows:

A B C 37% Formaldehyde 1000 cc 1000 cc 2000 cc Water 4000 cc 4000 cc 4000 cc Ammonium Chloride 140 grains 280 grains 280 grains EXAMPLE 2. yarn is to be knitted, in which case yarns have recover- Using the general process and apparatus as described with respect to FIGS. 3 and 4, 100 percent cotton yarn having a cotton count of 10/5 was again processed under the conditions shown in Table 2, with the yarn speed through the tubular conduit varying between 125 and 500 yards per minute and the processing temperature between 425 and 460F. The control, designated Sample No. l, is included for comparison.

graft copolymers may be prepared by the injection of TABLE II 100% COTTON 10/5 COTTON COUNT WET SPL OR AIR 120 YD. WT. STRENGTH HAND RATING NO. YPM F. DRY PSI GRAINS GRAMS ELONCU" Mo L Ma Aver.

1 101 645.1 8.22 l0 l0 10 10 2 125 425 DRY 10/2 97 697.0 7.72 6 7 l 5 3 125 425 WATER 10/2 97 628.4 7.28 3 l 2 2 4 125 425 WET 10/2 97 618.2 7.64 7 8 6 7 5 300 425 WET l0/2 98 583.7 7.86 2 2 4 3 6 500 425 WET 12/2 98 597.5 7.62 8 9 7 8 7 500 440 WET 12/2 98 694.5 8.70 4 3 3 3 8 500 460 WET 12/2 103 789.9 9.28 5 4 8 6 9 500 440 DRY 12/2 103 761.8 9.34 9 5 9 8 10" 500 460 DRY 12/2 103 757.6 9.25 1 6 5 4 Solution Formulation:

3% lb. cones run on 2/4/71 and same skein weight obtained (18% shrinkage).

2000 cc 37% Formaldehyde 4000 cc Water Individual Raters: Mo

280 Grains Ammonium Chloride L "Description of Instron used:

As shown by the results of Table 2, the treated yarn generally showed an increase in tensile strength and elongation. The treated yarn also generally exhibited acceptable hand, comparing favorably with the untreated Sample No. 1. Samples No. 8 and 10 which were processed at 460F. and 500 yards per minute yarn speed suffered only slightly in hand and produced the best values for percent elongation and strength.

As shown by the foregoing results, cotton yarn processed in accordance with the present invention demonstrates an increase in both tensile strength and elongation. The simultaneous increases of tensile strength and elongation is unusual and unexpected, since the heat treatment produces a more ordered structure which is inconsistent with an increase in elongation. The explanation for such results is not clearly understood but is believed to be related to the relaxation of the yarn structure occurring due to the yarn being heated in the absence of substantial yarn tension, which releases the locked-in stresses in the fibers and yarn. The

release of stress is particularly significant where the 8" Cell: 10" Gage; 6.0"lmin X hd sp: 12.0"/min chart sp: 1000 grams FSL an inert gas such as nitrogen in the yarn tube (FIGS. 3 and 4) along with the heated air and a gaseous monomer such as an acrplic acrylic Similarly, gases may be injected with the heated air to create sites within the yarn to enhance moisture regain, dyeability and soil release properties. A coating to affect the flamability of the yarn may also be applied around the fibers.

We claim:

1. A continuous process of heat treating cotton yarn to increase the tensile strength and elongation thereof, comprising passing said yarn through a tubular convoluted conduit to heat such yarn to a temperature above its shrinkage temperature but less than its degradation temperature in the absence of substantial tension on said yarn, permitting said heated yarn to shrink without substantial tension on said yarn and subsequently cooling said yarn to set the same.

2. The process of claim 1 in which said yarn is heated by the application of radiant heat.

3. The process of claim 1 in which said yarn is exposed to a temperature within the range of from about 5. A process of heat treating cotton yarn to improve the strength and elongation thereof, comprising passing said yarn through a first nozzle and tubular convoluted conduit, contacting said yarn within said nozzle with heated air to cause said yarn to pass through said nozzle and said tubular conduit, heating said yarn within said tubular conduit in the absence of substantial tension on said yarn by the application of heat to a temperature above its shrinkage temperature but less than its degradation temperature, permitting said heated yarn to shrink without substantial tension on said yarn, and subsequently removing said yarn from said tubular conduit and cooling said yarn to set the same.

8 6. The process of claim 5 in which said yarn is passed through a second nozzle upon exiting from said tubular conduit and is contacted with cold air within said second nozzle to facilitate cooling and setting of said yarn.

7. The process of claim 5 in which said yarn is exposed to a temperature within the range of from about 400F. to about 460F. for a period of time of approximately 5 to about 10 seconds.

8. The process of claim 5 in which said heated air is at a temperature of from approximately 200F. to about 500F. and at a pressure of about 5 to about 20 psig.

9. The process of claim 8 in which said yarn is passed through said first nozzle and tubular conduit at a speed of from approximately 50 to about 500 yards per minute. 

1. A continuous process of heat treating cotton yarn to increase the tensile strength and elongation thereof, comprising passing said yarn through a tubular convoluted conduit to heat such yarn to a temperature above its shrinkage temperature but less than its degradation temperature in the absence of substantial tension on said yarn, permitting said heated yarn to shrink without substantial tension on said yarn and subsequently cooling said yarn to set the same.
 2. The process of claim 1 in which said yarn is heated by the application of radiant heat.
 3. The process of claim 1 in which said yarn is exposed to a temperature within the range of from about 400*F. to about 460*F for a period of time from about 5 to about 10 seconds.
 4. The process of claim 1 in which said yarn is impregnated with a chemical solution prior to heating to help prevent degradation of said yarn.
 5. A process of heat treating cotton yarn to improve the strength and elongation thereof, comprising passing said yarn through a first nozzle and tubular convoluted conduit, contacting said yarn within said nozzle with heated air to cause said yarn to pass through said nozzle and said tubular conduit, heating said yarn within said tubular conduit in the absence of Substantial tension on said yarn by the application of heat to a temperature above its shrinkage temperature but less than its degradation temperature, permitting said heated yarn to shrink without substantial tension on said yarn, and subsequently removing said yarn from said tubular conduit and cooling said yarn to set the same.
 6. The process of claim 5 in which said yarn is passed through a second nozzle upon exiting from said tubular conduit and is contacted with cold air within said second nozzle to facilitate cooling and setting of said yarn.
 7. The process of claim 5 in which said yarn is exposed to a temperature within the range of from about 400*F. to about 460*F. for a period of time of approximately 5 to about 10 seconds.
 8. The process of claim 5 in which said heated air is at a temperature of from approximately 200*F. to about 500*F. and at a pressure of about 5 to about 20 psig.
 9. The process of claim 8 in which said yarn is passed through said first nozzle and tubular conduit at a speed of from approximately 50 to about 500 yards per minute. 